Spatial separation of ion clouds between sympathetically laser-cooled Cd+-ion isotopes in a Penning trap

Natural Cd+ ions in a Penning trap are cooled sympathetically below 1 K by a Coulomb interaction with directly laser-cooled Be+ ions. Spatial separation of the Be+ and Cd+ ion clouds due to centrifugal force is observed directly. When the frequency of rotation of the ion clouds is accelerated, the separation between Cd+-ion isotopes (A = 110 and 116) can be clearly observed, though their mass difference is very small. The equations of motion for 100 Be+ ions and 50 Cd+ ions are solved to simulate the experiments, and the result shows the spatial separation between the two ion species. The separation between the Cd+-ion isotopes is investigated by comparing the experimental results with numerical calculations.